Railway traffic controlling apparatus



29, F. H. NICHOLSON 1,924,215

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed 001;. 1'7, 1952 N 5 i w= L & m a; wi R Lb 5 u:

' INVENTOR. Fran ll. M'clzolsolz.

HIS ATTORNEY.

Patented Au 29, 1933 i RAILWAY TRAFFIC CONTROLLING APPA-Z a RATUS,

H; Nicholson,- Edgewood, Pa., assignor to The Union Switch & Signal Company; Swissvale, Pa'., a Corporation of Pennsylvania Application October 17, 1932. Serial No. 638,062 7 Claims. 2 (01. 246-63) i My invention relates to railway traffic control-' ling apparatus of the type employing alternating current track circuits and locomotive-carried cab signaling equipment and more particularly to apparatus for automatically changing the electric tuning of the train-carried cab signaling equip-' ment whenthe locomotive leaves a track sectionsupplied with current of a given frequency and enters a track section supplied with current of a different frequency. I

I will describe one form of apparatus, em-

bodying my invention, and will then the novel features thereof in claims. Fig. 1 of the accompanying'drawing is a diapoint out grammatic view of the train-carried portion of the cab signaling equipment, showing one form of automatic tuning-change apparatus embodying my invention. Fig; 2 is a diagrammatic view 1 of a section of railway track showing a portion of the wayside signaling equipment. V

In train control systemsof the coded track circuit type,'it is the usualpractice to employ a track circuit current having; a frequency in the order of60or 100 cycles per second, referred to as the carrier frequency,this current being in-.

terrupted periodically at different' rates which aredetermined by .traiiic conditions inadvance of the train, these rates orcode speeds being translated by the train-carried equipment ,into

a 'appropriate cab signals aboard the"locomotive.

In non-electrified territory, or in territory wheredirect propulsion. current or alternating propulsion current comparatively free from barmonics' is used, a carrier frequency of 100. cycles per second has been found to be highly satisfactoryrfrom the standpoint of safe and reliable train operation. However, where the alternating propulsion current contains prominent 'harmonies. of the even series, or of the usual odd'series, or both, there is danger of interference with the display of proper cab signal indications caused by beat frequencies arising from modulation of the carrier current by the above harmonies, thesebeat frequencies approaching the code speeds normally used for initiating cab sig nal indications. The even harmonics may arise from directcurrent saturation of the locomotive transformers caused by directpropulsion current in territory where both alternating current and direct current propulsion aroused; If the'propulsion current'is' 25 cycles; and the third and fourth harmonics are p'romin ent a carrier fre quency of 81 cycles, forexample,half-way'between these harmonics; may provide a high.de'-.

gree ofzimmunityjfromiinterference, the beat cally reversed voltages, in step with the code,'in

notes arising from the use of this frequency being sufficiently far removed from-jthe code speeds to preventtr'anslation into cab indications by the decodingequipmentr j ie f In order that the same locomotive may operate over certain track circuits suppliedwithcode carrier current of one frequency,- as well as over other track circuits in which the carriercurrent frequency is different; it becomes. desirable to provide automatic tuning-change"apparatus; one form of which will-now be described. ,ItwilL'of course, be understood that the tuning-change; apparatus embodying my invention can be used as" well in connection with a given track circuit which is capable of; being supplied,v atdifierenta times with carrier current ofonexor another freq r Referring toFigs. land 2 of the drawing, it will first be assumed that thelocomotive occupies *section DE in which the rails' 1 and2 are supplied with periodically interrupted or-coded currentof cycle carrier frequency from a transformer T The rail flux set up by this current will; induce cumulative voltages in the receiver windings 3 and 4; the resultantvoltage being applied, by means of step-up transformer T to the grid of the first stage amplifier tube VTl'. The outputbf tube VTl passes through interstage transformer T and is'- applied to-the grid of detector. tube VT2, so that unidirectional output current pulses, corresponding to the on; code" impulses in rails' 1 and 2, will exist in the primary; winding 5 ofv master relay transformer T to induce periodiwinding 6 oftransformer T Therefore, armature 7 of polarized master relay MR will operate to and fro, applying direct current from a source B-C, alternately, firstItoIone and then to; the other half of primary winding 8' of transformer As a result, an alternating voltage ofthe track circuitcode frequency will be induced in the secondary winding ,9 of this transformer,-and,' depending upon' the particular code speedas determined' by traflic conditions, one or theother of the code-selective relays R orfR. willbecome, energized to energize cab signal S or S respec tively., l I a,

The condensers C and C are used'to tune the receiver circuit involving receiver windings 3 and 4 and transformer T so that 100 cyclegcarrier' current will be passed freely into tube VT1, .'cur,-" rents of other frequencies being :effectiv'ely,

blocked, in order to eliminate stray power sources.

ca v

/ frequency will be blocked by the receiver circuit in the condition illustrated, both relays R and R will become deenergized, and a circuit foroperating motor M will become closedv at back contacts 10 and 11 of relays R and R ing, motor M will rotate cam N which, in turn, will cause contacts 13-14 and 13-15 to close alternately, energizing first one .and then the other of the two opposed windings of n the polarized relay PR,so that contacts 16-17 and 18-19 of relay PR. will become closed, and-willtendto close and open alternately, in step with the movement of the projections on cam N- a j The closing of contacts 16-17 and 18-19, which are design'edto remain in the last operated position until relay PR is reversed, connects condensers C and C in multiple with receiver tuning condensers C1 and C respectively, thereby changing the tuning of the receiver so thatit will pass freely currents of 87 cycle frequency, but will effectively block currents of other frequencies. 1 If the time interval during which contacts 16-17 and 18-19 remain closed is'made sufii'ciently long as com-pared with the time required fora code impulse in rails- 1 and 2' to become translated into an operating impulse in one or the other of relays ,R or R the result will be that contact 10 or 11 of relay R or R will open, whereas, contacts 16-17 and 18-19' of relay PR will remain closed .in' the 87 cycle position because operating energy has been disconnected froni=relay PR and the'contacts of this relay will remain in the last operated position, When this occurs, the apparatus will have become automatically conditioned for operation by rail current of 87 cycle carrier frequency.

When the locomotive reenters upon a track section supplied with current of IOO-cycle frequency,

or the frequency is restored from 87 to 100 cycles,- relays R and R will again both become 'deerier'gi'z'ed; and motor M will operate tocause contacts 16-17 and 18-19 of relayPR to open,

thereby restoring the receiver to the condition in which it will respond to 100 cycle current. Relay R or R will then pick up, disconnecting the source of energy for relay PR and contacts 16-17 and 18-19 will remain open.

The use of the two frequencies of 100 and 87 cycles is merely illustrative,- as the tuning-change apparatus embodyingmy invention can be adapted for use with any pair of suitable frequencies. Also, it is not necessary that the effective capacity of both condensers C andC be changed,

as a change in one or the other of these capacities, by the'addition of either multiple or series capacity, as may be required by the particular 3 carrier current frequency being used, may be sufli- ,cient. Furthermore, instead of introducing capaclty into the receiver circuit, the contacts 16- 17 and 18-19 may be used to introduce reactance or resistance into the receiver circuit, orto short- 76: circuit portions of the existing receiver-tuning impedances,cr,rearrange the connections of the tuningelements, It is not essential that therelay PR be emplayed, as'contact 13, or a pair of suchcontac'ts insulated from wire 12, can be used torepla'ce con-- tacts 16-17 and 18-19 of relay PR. Also,- 'in- Inope'rat- I "'vention, it is understood, that various changes stead of motor M and cam N, a reciprocating or flashing relay of any suitable; type, having a pair .of contacts which'become alternately closedjand opened at a relatively slow rate, when the relay becomes energized by the release of both relays R and R ,can be used to connect the condensers C? andC into the receiver circuit. The advantage obtained by using a polarized relay such as PR is that contacts 16 and 17 will remain in the I last operated position. l Although I have herein shown and described only one'forr'nof apparatus embodying my in- I and modifications-maybe made therein within thescope .ofthe appended claims without departing from the spirit and scope of my invention.

Having thus describedmy invention, whatiI claim is: l i V f 1. In combination, a stretch of railway track the rails of which are supplied with current of a first frequency, a ,train' control receiverin inductive relation with said rails and tuned for admitrent of a first frequency and at other times withcurrent of asecond frequency, a train control receiver in inductive relation with the rails of saidtrack and capable of being tuned for admitting induced current of either said first or said second frequency, a train governing device controlled by current of either said'first or said second frequency induced in said receiver which assumes a first or a second condition iniaccordance with. the

presence or absence respectively of induced .cur-

rent of said .first or said second frequency, andmeans controlled by said device when the device assumes said second condition for automatically altering the electric tuning of said receiver to admit inducedcurrent of said second or'said first frequency according as the rails were supplied with current of saidfirst or said second frequency respectively immediately before said device assumedsaid second condition.

3.'In combination, a stretch ofcrailway track the rails of which are normally supplied with current of a first frequency and are at times supplied with current of a second frequency,'a fre-' quency selective train governingdevice normally controlled by rail current of said firstfrequency and capable of assuming a first or a second condition inaccordance with the presence'or absence respectively of current "of said first frequency in the rails,'and' means governed by said device when the device assumes'said second condition for auto-.

matically conditioning said device for selective control by rail current of said second frequency;

4. In combination, a train control receiver capable of being adjusted to one or another of two conditions of tuning to passinduced current of one or another of two rail current frequencies respectively, a trafiicgoverning device controlled by the current induced in said receiver in such ,manner as to assume' a first'condition whenin duced' current of-either of said'two frequencies" is present in the receiver andto assume asecond condition when saidinduced current is absent,

and means governed by saiddevice when the device assumes said second condition for automatically and alternately adjusting the tuning of said receiver from said one to said other condition at predetermined time intervals until the frequency for which said receiver is tuned corre-,

sponds to the rail current; frequency whereupon said device will assume said firstcondition.

5. In combination, a stretch of railway track the rails of which are at times supplied with current of a first frequency andflat other times with current of a second frequency, a frequency selective train governing'device controlled by rail current of said first or said second frequency in such manner as to assume a first condition ac cording as'said device is conditioned for selective control by rail current of said first or said second frequency respectively, said 'device assuming a second condition when the rail current is interrupted for a prolonged time interval, and means governed by said devicewhen the device assumes said second condition for alternately conditioning said device for selective control by rail current of said first and of said second frequency respectively.

6. In combination, a stretch of railway track the rails of which are supplied with current of a first frequency, a train control receiver in inductive relation with the rails of said track and having an electric filter capable of selectively passing induced current of said first frequency,

a traflic governing device controlled by said inducedcurrent which assumes an energized or a deenergized condition according as said induced current is present or absent, a contact'controlled by saiddevice which becomes closed periodically when the device is deenergized, and means con- 7 trolled by said contact in itsclosed position for altering the electric 'tuning of said filter to pass j induced current of a second frequency thereby conditioning-said receiver for control of said de-' vice by induced current of said second frequency.- 7. In combination, a stretch of railway track the rails of whichare supplied with current of a first frequency, a train control. receiver in'inductive relation with the rails of said track and having an electric filter'capable of selectively .passing induced current of said first frequency,

a traffic governing device controlled by said induced current which assumes an energized or a deenergized condition according as said induced 0nd frequency to control said device, and apole changer governed by said motor and effective for periodically pole-changing said relay while said motor is energized.

FRANK H. NICHOLSON. 

